6 inch wall cavity-which insulation type

bauney

Hi all,
I need to some help on deciding the insulation type for my house.I'm starting the blocks shortly so need to decide on the insulation type. I've spoken to my engineer, insulation companies, SEAI and other building professionals. All of which have different opinions and facts......:-(

I will have a 6 inch wall cavity in which i need to insulate.

Should i blow insulation in the cavity?
Should I fully fill the cavity with 6 inches of insulation board?
Should i partially fill the cavity with 4 inches of insulation board?

Cosy boards-
Should i put the50mm cosy boards (or dryline boards) on the internal side of the external walls also? I heard the positives and negatives on this also.

I plan to have underfloor heating (with aerothermal) with a large open area living.The floor will have 150 mm insulation.
I hope to have a well insulated house and am aware of the costs of all of these extra mm(s) of insulation. So please,let me know what you think is best?

My head is ready to burst!!!!:mad:

Redfowler11

In a similar situation. Going to go for 100mm insulation in a 150mm cavity (block wall construction) Not convinced by the full cavity fill particularly with the weather in Ireland. Going to use cosy board on internal walls as well. Aiming for around 0.15 u value.

kboc

Full fill bead is the job. By far the easiest to ensure a quality job and this is what I done. Stops water ingress across cavity and there is no free cavity for air to whistle round in and create a draft at wall plate level etc, although it is not airtight in itself. Boards are a disaster if brickie couldn't care less

Poor Uncle Tom

kboc wrote: »

Full fill bead is the job. By far the easiest to ensure a quality job and this is what I done. Stops water ingress across cavity and there is no free cavity for air to whistle round in and create a draft at wall plate level etc, although it is not airtight in itself. Boards are a disaster if brickie couldn't care less

The asumption here is that a 'brickie' couldn't care less but the 'pump guy' for the insulation company is constructions answer to Dr. Phil.

If both act as professionals and do their jobs properly then full fill board is better than pumped, imo, as you will never get the cavity pumped with bead to the pressure and density of the board.

gear_ie

Building a block house next year and I am concerned that I will not have the correct level of insulation. Looking at the drawings we will have the following specifications:

Foundations:
75mm screed finish on two layers of 75mm 'Xthratherm Insulation on 150mm concrete. DPC on 50 mm sand blinding on 300 mm min. graded hardcore, well consolidated. 25 mm extruded polystyrene board f.r.a. dressed down vertically at edges as perimeter insulation. 12 mm expansion joint between edge of concrete base and face of wall using joint filler, polythene foam strip and sealed with mastic.

Walls:
External wall to be 100mm concrete block outer leaf, 100mm 'Xtratherm' CavityTherm CT/PIR insulation, 100mm or 215mm concrete block, 6mm Gypsum-based parge coat, With gypsum plaster finish.

Attic (roof void):
Provide 150 mm thick mineral wool quilt insulation laid in the roof space between ceiling joists without compression. There should then be an additional layer of 150mm mineral wool insulation laid counter wise across the ceiling joists. Care should be taken to ensure that all gaps and void are well filled to ensure that is no heat leakage from voids. 'Xtratherm' 42.5mm sr/tb-mf liner to screw fixed to the underside of the ceiling and skimmed.
Attic (sloping ceiling):
125mm 'Xtratherm' rafterloc fitted between rafters fixed flush with the underside of the ceiling rafter, 'Xtratherm' 42.5mm sr/tb-mf liner to screw fixed to the underside of the ceiling and skimmed.

The house is specified to be airtight with ventilation supplied by MVHR and I will be asking the Arch for u-levels for walls / foundation / roof as well as DEAP calcs for energy usage, but in the meantime can someone tell me if the insulation levels being specified will be adequate.

Thanks!

beyondpassive

gear_ie wrote: »

Building a block house next year and I am concerned that I will not have the correct level of insulation. Looking at the drawings we will have the following specifications:
!

You really couldn't tell if that is sufficient, It may just comply with Part L 2008 but wouldn't come near Part L 2011 (if you submit planning before Dec 2011 and build to wallplate by June 2013 you can use the 2008 regs,) You really should have a BER or preferably a PHPP done at this stage to model the running costs of the build. It would be a bad idea to just comply with regulations as they dont factor in bad insulating and airtightness practice among Irish builders which means building running cost are likely to be as much as twice what the BER would suggest.

The amount of insulation depends on the shape factor of the building, Is it compact and well orientated to make the most of solar gain.
Are you designing the specification to try and keep the temperature of the structure as high as possible during the year, using solar heat fed through the underfloor to 'charge' the slabs in Autumn. Or are you just puttin in a big boiler to come on for a couple of hours twice or three times a day. How are you dealing with cold bridges at rising walls, eaves, gables and window/door placements.

gear_ie

I plan on making the most of solar gain with the house 'L' shaped and having large windows south / south-west facing. My aim is to have a house that heats itself mostly - I don't want a big gas/oil boiler but also don't want to spend a fortune on a HP system as I don't see the return on investment for quite some-time. I will also be planning on doing 2 blower door tests to ensure air-tightness during the build and to find areas of heat loss.

In regards to Cold bridging this is from the tender document:

Cold bridging:
All window & door jamb shall have ‘XtraTherm Close-R, head & cill details shall have 25 mm thick expanded polystyrene insulation (thermal resistance through of not less than 0.45m K/W) to prevent any cold bridges occurring. Insulation at windows & door jambs shall be 150 mm wide as dpc to allow 50 mm overlap with cavity wall insulation. As per the appendices, the approved details for cold bridging and sealing should be adopted.

kboc

I am very interested by your tender document, do you mind if I could have a look at it, obviously with sensitive info removed.

Thanks

gear_ie

beyondpassive wrote: »

You really couldn't tell if that is sufficient, It may just comply with Part L 2008 but wouldn't come near Part L 2011 (if you submit planning before Dec 2011 and build to wallplate by June 2013 you can use the 2008 regs,)

I asked the Arch and was told that the design & specifications complied with Part L of the 2011 Building Regs.

esox28

25 mm extruded polystyrene board f.r.a. dressed down vertically at edges as perimeter insulation. 12 mm expansion joint between edge of concrete base and face of wall using joint filler, polythene foam strip and sealed with mastic

hey gear,

would be very great-full if you could break down this foundation flooring detail for me, cant get the picture in my mind.
I understand you are using eps for your perimeter insulation, but what is the 12mm expansiion joint in the floor for?

many thanks